1. Field
Aspects of the present invention relate to a secondary battery module.
2. Description of the Related Art
A secondary battery module usually includes a plurality of secondary batteries connected in parallel/series as unit cells. Each of the unit cells includes an electrode assembly having a positive electrode and a negative electrode with a separator positioned therebetween, a case having a space to receive the electrode assembly therein, a cap assembly coupled to the case and sealing the case, and positive and negative terminals protruding from the cap assembly and electrically connected to positive and negative current collectors provided in the electrode assembly.
In some instances, each of the unit cells has a membrane and a fuse installed to be electrically connected to the positive electrode terminal. The membrane makes contact with the negative electrode terminal when the internal pressure of the case increases due to overcharge of the unit cell, and creates short circuit between the positive and negative electrodes. When short circuit is created, the fuse is cut off, thereby blocking an electrical connection of the unit cell.
As the number of secondary batteries included in a battery module increases, the number of membranes and fuses to be installed also increase, thereby increasing a probability of malfunction of an overcharge preventing safety device. Even during normal operation, most of the unit cells included in the secondary battery module may be unavoidably damaged.